Tuberculosis (TB) is a highly infectious airborne disease caused by the widely spread pathogen Mycobacterium tuberculosis (Mtb), infecting around one-third of the world's population and claiming the lives of 1.5 million each year. The worldwide emergence of multidrug-resistance tuberculosis (MDR-TB), extensively drug-resistant tuberculosis (XDR-TB), and totally drug-resistant tuberculosis (TDR-TB) further worsens this global health crisis. An important step in containing the spread of this deadly airborne disease is rapid, timely detection and diagnosis of Mtb, preferably at point-of-care (POC). However, the extremely slow growth rate of the virulent Mtb pathogen remains the largest hurdle to overcome. As a direct consequence, the gold standard culture-based technique for TB diagnosis is limited to patients with advanced infection and usually takes several weeks to produce a definitive diagnosis. Although nucleic acid-based diagnostic methods such as GeneXpert provide sensitive and specific diagnosis, the cost and requirement of highly skilled technical personnel and sophisticated instrument recalibration makes them less accessible in developing countries, where TB prevalence is highest.
One approach takes advantage of an enzyme expressed by Mtb, BlaC, as the biomarker for Mtb detection. BlaC is an Ambler class A β-lactamase that efficiently hydrolyzes β-lactam antibiotics and is central to the biochemical mechanism responsible for pervasive β-lactam-antibiotic resistance. Because the first β-lactamase was discovered in 1940, a large number of β-lactamases have been identified that can hydrolyze a variety of β-lactam antibiotics, from original penicillins, to cephalosporins, to the latest carbapenems. To assay the activity of β-lactamases, fluorogenic and luminogenic probes have been developed to take advantage of the high sensitivity of fluorescence and luminescence detection methods. However, most of these probes do not possess specificity for BlaC, and are broadly hydrolyzed by many β-lactamases, such as the common TEM-1 β-lactamase (TEM-1 Bla) in Gram-negative bacteria. Therefore, they are not suitable for Mtb diagnosis, because clinical materials can carry many other bacterial species that often express β-lactamases.
Despite the advances in the development of fluorescent probes for the detection of β-lactamase and the diagnosis of tuberculosis, a need exists for novel probes that facilitate the rapid detection of tuberculosis. The present invention seeks to fulfill this need and provides further related advantages.